Interest in the use of compressed natural gas (CNG) and liquid natural gas (LNG) as a motor vehicle fuel has increased dramatically in recent years. Whole fleets of government and industry vehicles have successfully been converted to natural gas, and some private individuals have converted their vehicles as well. Congress recently passed an energy bill which would require further increased use of alternative fuels in government and private fleets.
Several factors have influenced this increasing interest in natural gas as a motor vehicle fuel. Natural gas burns cleaner than traditional motor vehicle fuels. Using natural gas in motor vehicles thus lowers vehicle emissions dramatically, reducing the environmental impact of motor vehicles. Engines burning natural gas also remain cleaner longer, which results in less wear on the engine, less degradation of fuel efficiency and emissions cleanliness over time, and less frequent and lower service and repair costs. Also, natural gas is a relatively cheap and plentiful natural resource within the United States.
A limiting factor in the expanding use of natural gas as a motor vehicle fuel has been the availability of natural gas filling stations. Current stations are expensive to construct and operate. The expense and inefficiency of current refueling stations has prevented widespread conversion to natural gas, especially by private individuals. Fleet conversions are more economically viable because of the large number of vehicles that are consistently refueled at one central location. But private individuals often have no access to a natural gas refueling station, or their access is limited to fleet refueling stations that also sell to private customers. These fleet refueling stations are found only in larger metropolitan centers, effectively restricting the range of private users' vehicles. Thus there is a need for a less expensive, more efficient natural gas fueling station so that more such stations can be constructed and operated, better meeting the needs of private individuals as well as fleet owners who would like to convert their vehicles to natural gas.
Natural gas powered vehicles store the natural gas in their tanks as either compressed natural gas (CNG) or liquid natural gas (LNG). Current LNG filling stations dispense LNG from LNG storage tanks which are supplied by LNG tanker trucks. Current CNG filling stations take natural gas from a natural gas pipeline, compress it, and store it in high-pressure storage tanks from which it is dispensed. The compression requires large amounts of equipment and energy, significantly increasing the cost of the station and the CNG it supplies. A second problem is that natural gas from pipelines is only about 80% pure. Purification procedures are not easily able to eliminate the contamination found in natural gas pipelines. Without expensive purification procedures, the natural gas is not pure enough to burn cleanly, and the major benefits of natural gas are lost. With expensive purification procedures, the CNG cannot be priced competitively with other fuels. A third problem is CNG stations using existing technology can only be located in areas serviced by natural gas pipelines.